KR20130032377A - Aqueous solution capable of absorbing and collecting carbon dioxide in exhaust gas with high efficiency - Google Patents

Abstract

(식 중, R은 탄소수 3 내지 5의 직쇄상 또는 분지쇄상의 알킬기를 나타냄)Disclosed herein is an aqueous solution for absorbing and recovering carbon dioxide from a gas containing carbon dioxide, the aqueous solution comprising 50 to 70% by weight of a secondary amine compound represented by the formula (1) and a surfactant , And a carbon dioxide absorption and recovery method using the aqueous solution.
≪ Formula 1 >

(Wherein R represents a linear or branched alkyl group having 3 to 5 carbon atoms)

Description

Aqueous solution that efficiently absorbs and recovers carbon dioxide in exhaust gas {AQUEOUS SOLUTION CAPABLE OF ABSORBING AND COLLECTING CARBON DIOXIDE IN EXHAUST GAS WITH HIGH EFFICIENCY}

The present invention relates to an aqueous solution for absorbing and recovering carbon dioxide (CO ₂ ) contained in the gas. The present invention also relates to a method for absorbing and recovering carbon dioxide using the aqueous solution.

Recently, climate fluctuations and disasters, which are thought to be caused by global warming, have an enormous impact on agricultural production, residential environment and energy consumption. This global warming is believed to be due to the increase in greenhouse gases, such as carbon dioxide, methane, nitrous oxide, and freon, which increase as human activities become more active. Carbon dioxide in the atmosphere is the most important of the greenhouse gases, and measures for reducing the amount of emission are urgently needed.

Sources of carbon dioxide are coal-fired power plants that use coal, heavy oil, and natural gas as fuels, boilers in manufacturing plants, kilns in cement plants, furnaces in steel mills that reduce iron oxides from coke, and cars using gasoline, heavy oil, and diesel. And transportation equipment such as ships and aircrafts. Among these, except for a transportation device, it is expected to be a stationary facility and a facility which is easy to implement measures to reduce the emission of carbon dioxide.

Several methods are known to recover carbon dioxide in exhaust gas. And now a wide variety of methods are being studied.

For example, a method of absorbing carbon dioxide by contacting a gas containing carbon dioxide with an aqueous solution of alkanolamine in an absorption tower is well known. The alkanolamines here include monoethanolamine (hereinafter sometimes referred to as MEA), diethanolamine (DEA), triethanolamine (TEA), methyldiethanolamine (MDEA), diisopropanolamine (DIPA), diglycol Amines (DGA) and the like are known, but MEA is usually used.

However, when the aqueous solution of these alkanolamines is used as the absorbent liquid, since the corrosiveness of the device material is high, it is necessary to use expensive corrosion resistant steel for the device or to lower the amine concentration in the absorbent liquid. In addition, since it is difficult to desorb the absorbed carbon dioxide, it is necessary to heat the temperature of the desorption to a high temperature of 120 ° C. so that desorption and recovery are performed. _It is high as ₂ , and high energy is necessary for desorbing carbon dioxide due to this. For example, in order to recover carbon dioxide from a power plant using this method, about 20% of the amount of power generated requires extra energy. In an era in which reduction of carbon dioxide generation, energy saving, and resource saving are required, this high energy consumption is a major factor preventing the practical use of carbon dioxide absorption and recovery facilities, and a technology for recovering carbon dioxide at low energy is required.

For example, Patent Document 1 discloses removal of carbon dioxide in fuel exhaust gas by contacting an aqueous solution of a so-called hindered amine having steric hindrance, such as an alkyl group, around an amino group with a combustion exhaust gas under atmospheric pressure, and absorbing carbon dioxide in the aqueous solution. The method is described.

Patent Document 1 describes examples of 2-methylaminoethanol (hereinafter sometimes referred to as MAE) and 2-ethylaminoethanol (hereinafter sometimes referred to as EAE) as hindered amines. MAE and EAE 30% by weight of an aqueous solution is used in the examples. Although there is no example, amines, such as 2-isopropylamino ethanol (henceforth IPAE) may be described as another hindered amine.

Patent Literature 2 likewise describes an absorbent liquid containing only 2-isopropylaminoethanol (IPAE), which is a hindered amine, and is characterized by high absorption performance and desorption performance, but as shown in Comparative Examples 1 and 2, It is described that increasing the concentration to 60% by weight in order to recover the carbon dioxide more effectively results in a decrease in the absorption rate and a decrease in the desorption amount, so that the properties of the hindered amine cannot be utilized and the performance of the absorbent liquid is lowered.

As for the amine component which is an active ingredient of a carbon dioxide absorption liquid, 3-5 mol / L and 35-50% by weight concentration are shown by most Examples, and it is known that use at high concentration reduces the overall performance. . As a cause, when the density | concentration in the absorbent liquid of an amine component is high, the viscosity of an absorbent liquid rises, especially the fall of absorption speed performance is considered, the heat transfer performance falls by the viscosity improvement, etc. are considered.

On the other hand, since the recovery amount of carbon dioxide in one cycle of the absorption step and the dissipation step is increased by the improvement of the amine concentration in the absorbent liquid, when the high concentration can be achieved, there is an advantage of reducing the recovery energy per unit weight.

In addition, Patent Document 3 discloses that when carbonic acid gas is recovered by microbubble and stored in the seabed or in the ground, a surfactant may be mixed to prevent the microbubbles from being bonded to each other and to extend the life of the microbubbles. , The effect of the surfactant is also different from the application and the effect in the alkanolamine aqueous solution like the present invention.

Japanese Patent No. 2871334 Japanese Patent Publication No. 2009-6275 Japanese Patent Laid-Open No. 2004-50167

In view of the above problems of the prior art, the present invention can not only absorb carbon dioxide in gas with high efficiency, but also can remove carbon dioxide from an aqueous solution that absorbs carbon dioxide with high efficiency, and can provide high purity carbon dioxide with low energy consumption. It is an object of the present invention to provide an aqueous solution which can recover. Specifically, by using an aqueous solution containing a high concentration of hindered amine as an absorbent liquid having better performance than the conventional one, carbon dioxide absorption and desorption amount per unit amount are large, and energy required for carbon dioxide desorption is low, thus efficiently absorbing carbon dioxide. It is also an object of the present invention to provide an aqueous solution capable of recovering high purity carbon dioxide by desorption.

In order to improve the efficiency at the time of absorption, the present inventors carried out the absorption process of carbon dioxide with an absorbent liquid containing a high concentration of various alkanolamines of the hindered amine type, and desorbs carbon dioxide from each absorbent liquid and recovers the carbon dioxide. The study was intensive.

As a result, when an absorbent liquid containing 50 to 70% by weight of N-alkylalkanolamine which is a hindered amine and a small amount of surfactant is used with respect to the exhaust gas containing carbon dioxide, the desorption process is continued after the absorption process. In addition, the high absorption amount and absorption rate of carbon dioxide are achieved, and it is possible to greatly improve the recovery amount in one cycle of absorption and desorption per unit absorption liquid amount. As a result, it has been found that the energy for separating and recovering carbon dioxide can be reduced, and the present invention has been completed.

In general, since most of the hindered amines have a structure in which a bulky alkyl group is substituted with an amino group, its hydrophilicity is low and when used at a high concentration, problems such as decrease in absorption amount and absorption rate due to improvement of viscosity Has been raised.

However, as a result of intensive examination of the relationship between the various physical properties and the absorption performance of the high concentration aqueous solution, the surface tension of the absorbent liquid and the absorbent liquid performance are related. In the absorbent liquid to which the surfactant is added, the surface tension of the absorbent liquid is lowered by the addition of the surfactant. As a result, it was found that the absorption rate can be prevented from being lowered even in a high concentration of the absorption liquid. As a result of measuring the relationship between the addition of various surfactants and the absorption performance, the surface tension of the absorbent liquid at room temperature (25 ° C) should be 30 mN / m or less in order to suppress the decrease in the absorption rate in a high concentration region than conventionally. We found a need.

As a result, the conventional problem is solved, and the absorption amount is increased, and the absorbent performance of a large loading amount, which is the difference between the absorption amount and the desorption amount in one cycle, is expressed, and carbon dioxide can be recovered or desorbed with lower energy than the conventional one, thereby recovering high purity carbon dioxide. It has become possible to provide an aqueous solution.

That is, this invention comprises the structure of the following items 1-7.

Item 1. An aqueous solution for absorbing and recovering carbon dioxide from a gas containing carbon dioxide, the aqueous solution comprising 50 to 70% by weight of a secondary amine compound represented by the formula (1) and a surfactant.

(Wherein R represents a linear or branched alkyl group having 3 to 5 carbon atoms)

Item 2. The aqueous solution according to Item 1, wherein the weight concentration of the surfactant is 10 to 1500 ppm.

Item 3. The aqueous solution according to Item 1 or 2, wherein R is an isopropyl group or n-butyl group, and the surfactant is a compound having a nonionic perfluoroalkyl group.

Item 4. The aqueous solution according to Item 1 or 2, wherein R is an isopropyl group or n-butyl group, and the surfactant is a compound having an amphoteric perfluoroalkyl group.

Item 5. The aqueous solution according to Item 1 or 2, wherein R is an isopropyl group or n-butyl group, and the surfactant is a nonionic polyoxyethylene alkyl ether compound.

Item 6. The aqueous solution according to any one of Items 1 to 5, wherein the surface tension at 25 ° C is 30 mN / m or less.

Item 7. (1) A step of absorbing carbon dioxide from a gas by contacting the aqueous solution according to any one of items 1 to 6 with a gas containing carbon dioxide, and

(2) A step of desorption and recovery of carbon dioxide by heating the aqueous solution absorbed in carbon dioxide obtained in the above (1)

Carbon dioxide absorption and recovery method comprising a.

According to the aqueous solution of high concentration alkanolamine containing the surfactant of the present invention, not only the recovery amount of carbon dioxide per cycle of absorption and desorption increases, but when the high concentration absorption liquid is used, the calorific value per mole of carbon dioxide decreases compared to the low concentration absorption liquid. It is effective, and the recovery energy of carbon dioxide per unit weight is low. As a result, according to the aqueous solution of this invention, it becomes possible to absorb and desorb carbon dioxide in gas efficiently and with low energy consumption, and to collect | recover high purity carbon dioxide. Further, the efficiency of absorption and desorption of carbon dioxide leads to a decrease in the circulating flow rate in the absorption and desorption cycles, and it becomes possible to miniaturize absorption towers, desorptions, and the like and accompanying devices, resulting in a reduction in investment and operating costs. It comes in effect.

In addition, the monoethanolamine used for carbon dioxide absorption generally exhibits high corrosiveness to metal materials such as carbon steel, and especially corrosiveness is increased at high concentrations. However, the aqueous solution of N-alkylamines used in the present invention has low corrosiveness. Corrosion does not increase even at high concentrations, which is advantageous in that there is no need to use expensive, high quality corrosion resistant steel in plant construction.

Hereinafter, the present invention will be described in detail.

Aqueous solution for absorbing and recovering carbon dioxide

The aqueous solution for absorbing and recovering carbon dioxide from the gas containing carbon dioxide of the present invention is characterized in that it comprises 50 to 70% by weight of the secondary amine compound represented by the formula (1) and a surfactant.

≪ Formula 1 >

(Wherein R represents a linear or branched alkyl group having 3 to 5 carbon atoms)

Specifically, R includes n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, n-pentyl, isopentyl and the like, and R is preferably isopropyl, n-butyl and isobutyl More preferably isopropyl and n-butyl. Compound 1 may be included alone or in plural in the aqueous solution of the present invention.

The concentration of the secondary amine compound represented by the general formula (1) in the aqueous solution of the present invention is usually 50 to 70% by weight, preferably 52 to 70% by weight, more preferably 54 to 66% by weight. If it is 71 weight% or more, the effect of decreasing surface tension was also small and the effect of the absorption rate improvement hardly came out.

In general, the hindered amine is an excellent amine that exhibits low calorific value and high leaving property, unlike monoethanolamine, due to a difference in reaction with carbon dioxide. ¹³ C-NMR measurements indicate that the reaction between monoethanol and carbon dioxide is most often accompanied by carbamate bonds, with carbamate bonds and bicarbonates as long as R is a hindered amine of formula (1) It is known that all bonds are produced. For example, in ethylaminoethanolamine in which R is an ethyl group, carbamate bonds are about 30%, but in the compound 1 in which R is a linear or branched alkyl group having 3 to 5 carbon atoms, carbon dioxide and an amine compound The form of the bond with is a trace amount of carbamate bonds and most of the reaction with carbon dioxide is only a low calorific value bicarbonate bond. This leads to excellent performance in the task of reducing the recovery energy.

In addition, the aqueous solution of the present invention also has a feature that the amount of heat generated when absorbing carbon dioxide is smaller than that of the low concentration aqueous solution as described above. For example, the calorific value per mole when carbon dioxide is absorbed to a relative molar ratio of 0.6 mole from the beginning of the absorption reaction is 76.6 kJ / mol CO ₂ at an IPAE concentration of 30% by weight, whereas a high concentration of 60% by weight of IPAE concentration is obtained. In the case of, the value is low as 70.2 kJ / mol CO ₂ . The reason for this is that in the hindered amine structure of the present invention, the reaction between carbon dioxide and amine is mainly bicarbonate bond as described above, and the constituent of the calorific value is the formation of ion pairs of bicarbonate ions and protonated amines. And the solvent combination with water which is a solvent. In this case, it is estimated that a change will generate | occur | produce in the stabilization structure of each ion in the aqueous solution which contained the solvent sum by high concentration, and the fall of a calorific value is estimated.

In addition, since the calorific value of carbon dioxide absorption corresponds to the heat required at the time of carbon dioxide desorption, the energy consumption required for desorbing carbon dioxide can be suppressed low by the lowering of the calorific value, resulting in the effect of reducing the carbon dioxide recovery energy.

The effect and the kind about surfactant which are a component of this invention are demonstrated below. At high concentrations, the amine aqueous solution increases the amount of absorption and dissipation per unit weight of the absorbent liquid in one cycle, thereby reducing the recovery efficiency and energy recovery.As a high concentration reduces the contact efficiency of carbon dioxide and the absorbent liquid. As described above, the perceptual absorption rate is lowered and a predetermined amount of carbon dioxide cannot be achieved.

The present inventors examined in detail the relationship between the various physical properties of the highly concentrated absorbent liquid and the absorption rate of carbon dioxide, and found that surface tension is a dominant factor among the physical properties of the absorbent liquid. In the carbon dioxide absorption reaction by the amine aqueous solution, which is a gas-liquid contact reaction, the efficiency at the contact interface between gas and liquid is important, and it is estimated that the decrease in surface tension is involved in improving the contact efficiency in the high concentration absorption liquid.

The hindered amine of the present invention substitutes an amino group with an alkyl group. The longer the carbon chain of the alkyl group and the higher the degree of branching, the lower the hydrophilicity and the lower the solubility in water. For example, in patent document 2, when using IPAE whose R group is isopropyl, it is supposed that a speed fall occurs in the absorption liquid concentrated to 60 weight%.

In the case of IPAE, which is one of the compounds of the present invention, the absorption rate of the 30% by weight aqueous solution was 5.0 g / l / min in a predetermined absorption test, but was reduced to 2.9 g / l / min at 60% by weight. In the case of lowering the absorption rate in the high concentration absorption liquid, when 100 ppm of nonionic surfactant is added to the absorption liquid at a weight concentration, respectively, the absorption rate is 5.2 g / l / min at 30% by weight. However, when added to 60% by weight of the absorbent liquid, it was raised to 4.7 g / l / min, the effect of improving the absorption rate by the addition of the surfactant was seen. Here, the absorption rate indicates the amount of carbon dioxide absorption per minute at the time when the absorbent liquid is absorbed to half of the saturation amount when carbon dioxide is absorbed to the saturation amount at 40 ° C., and is 4.5 g / l / min or more industrially. It can be said that the absorption rate that can be employed.

The effect of surfactant in said high concentration amine aqueous solution is estimated as follows. The surface tension at room temperature when the surfactant is added to an aqueous solution of 30 to 60 wt% containing IPAE is 45 mN / m at 30 wt% (the surface tension of water not containing IPAE is 78 mN / m). At 60% by weight, it was 24 mN / m, which showed a large decrease in surface tension, which resulted in an improvement in absorption rate. This is presumed to be due to the improvement of the absorption rate in the improvement of "wetting" which promotes the contact efficiency of carbon dioxide and absorbent liquid on the surface of the absorbent liquid in gas-liquid reaction.

In general, the surfactant is classified into anionic, cationic, amphoteric and nonionic by the structure of the compound of the moiety exhibiting surfactant activity, but any of them can be used in the present invention. For example, the anionic ones include alkylbenzenesulfonic acid and monoalkyl phosphoric acid, and the cationic ones include alkyltrimethylammonium salts. As the nonionic one, polyoxyethylene alkyl ether (hereinafter sometimes referred to as PEG) or the like can be used. In addition, although the surfactant which has a fluorine atom in a compound can also be used for this invention, even if it is the said 4 types of classification according to the property of the part which shows surfactant, also any type of surfactant can be used. Examples of the fluorine-based surfactants include various commercially available surfactants containing perfluoroalkyl alcohol, perfluoroalkylsulfonic acid, and the like.

The surfactant used in the present invention is selected according to the kind of amine in the aqueous solution, the amine concentration, the temperature at the time of use, etc., but preferably a fluorine-containing compound and a polyoxyethylene alkyl ether compound are selected. As the fluorine-containing compound, a compound having a nonionic or amphoteric perfluoroalkyl group is particularly preferable. As a compound which has a nonionic perfluoroalkyl group, Sufflon S-141 (made by AGC Seimi Chemical Co., Ltd.) is mentioned, for example, As a compound which has an amphoteric perfluoroalkyl group, Suplon S -131 (made by AGC Seimi Chemical Co., Ltd.) is mentioned.

The optimum content of the surfactant in the aqueous solution of the present invention is selected depending on the type of amine used, the type of the surfactant, etc., but generally only a small amount is preferred, and preferably 10 to 1500 ppm, more preferably based on the weight of the aqueous solution. Preferably a range of 20 to 1000 ppm, more preferably 20 to 800 ppm, particularly preferably 30 to 700 ppm is selected. Although the optimum amount of surfactant is calculated | required by the test which changed the addition amount with respect to the absorption liquid from which the kind and concentration of an amine differ, when adding more than necessary, problems, such as foaming, arise. The surfactant may be added as it is, but may be added as a solution such as a solvent, such as alcohol, which does not affect absorption and desorption.

The secondary amine compound and the surfactant represented by the formula (1) can be obtained by obtaining a commercial item or by a known method.

The surface tension at 25 degrees C of the aqueous solution of this invention becomes like this. Preferably it is 30 mN / m or less, More preferably, it is 28 mN / m or less, More preferably, it is 20-27 mN / m. By setting surface tension to this range, the absorption rate of carbon dioxide in the aqueous solution containing the high concentration of amine of the present invention can be improved. Surface tension in this invention is made into the value measured at 25 degreeC by the pendant drop method using the Kyowa Kaimen Drop Master 300.

As gas containing carbon dioxide, for example, a thermal power plant using heavy oil, natural gas, or the like, a boiler in a manufacturing plant, a kiln in a cement plant, a blast furnace in a steel mill for reducing iron oxide with coke, or burning carbon in pig iron The exhaust gas from the converter of the same steel mill, etc. is mentioned, The carbon dioxide concentration in the said gas should just be about 5-30 volume% normally, especially about 6-25 volume%. In this carbon dioxide concentration range, the effect of the present invention is preferably exhibited. In addition, the gas containing carbon dioxide may include gases such as water vapor, CO, H ₂ S, COS, SO ₂ , and hydrogen in addition to carbon dioxide.

CO2 Absorption and Recovery Method

The method for absorbing and recovering carbon dioxide of the present invention is characterized by comprising the following steps:

(1) contacting the aqueous solution with a gas containing carbon dioxide to absorb carbon dioxide from the gas, and

(2) A step of removing and recovering carbon dioxide by heating an aqueous solution in which carbon dioxide is absorbed obtained in (1) above.

Carbon dioxide absorption process

The method of the present invention includes a step of absorbing carbon dioxide from a gas by contacting the aqueous solution with a gas containing carbon dioxide, but the gas containing carbon dioxide includes N-alkylaminoethanol which is a hindered amine represented by the formula (1). There is no limitation in particular in the method of carrying out contact absorption into the aqueous solution to carry out. For example, a method of bubbling and absorbing a gas containing carbon dioxide in this aqueous solution, a method of bringing the aqueous solution into a mist in a gas stream containing carbon dioxide (spraying or spraying), a filler made of magnet or metal mesh For example, the gas containing carbon dioxide and the aqueous solution are countercurrently contacted in the liver absorption tower.

The temperature at the time of absorbing the gas containing carbon dioxide in aqueous solution is normally performed at 60 degrees C or less, Preferably it is 50 degrees C or less, More preferably, it is performed at about 20-45 degreeC. The lower the temperature, the more the absorption is, but the extent to which the temperature is lowered is determined by the gas temperature of the exhaust gas, the heat recovery target, and the like. The pressure at the time of carbon dioxide absorption is usually performed at almost atmospheric pressure. It is also possible to pressurize to a higher pressure in order to increase the absorption performance, but it is preferable to carry out under atmospheric pressure in order to suppress the energy consumption required for compression.

The gas containing carbon dioxide is the same as described above.

·carbon dioxide Tally  fair

The method of the present invention includes a step of removing and recovering carbon dioxide by heating an aqueous solution obtained in the carbon dioxide absorption process.

As a method of desorbing carbon dioxide from an aqueous solution absorbing carbon dioxide and recovering pure or high concentrations of carbon dioxide, a method of heating the aqueous solution in the same manner as distillation to form a bubble in a kiln and removing it from a kiln, a bandung tower, a spray tower and And a method in which a liquid interface is widened and heated in a tallying tower containing a magnetic material or a metal mesh filler. As a result, carbon dioxide is liberated and released from the bicarbonate ion.

The liquid temperature at the time of carbon dioxide desorption is normally performed at 70 degreeC or more, Preferably it is 80 degreeC or more, More preferably, it is performed at about 90-120 degreeC. The higher the temperature, the higher the absorbed amount. However, the higher the temperature, the higher the energy required for heating the absorbent liquid. Therefore, the temperature is determined by the process gas temperature, heat recovery target, and the like. The aqueous amine solution after desorbing carbon dioxide is sent to the carbon dioxide absorption step again and recycled. In the meantime, the heat applied in the carbon dioxide desorption step is effectively used for the temperature increase of the aqueous solution by heat exchange with the aqueous solution directed from the carbon dioxide desorption step in the circulating process so that the energy of the entire recovery process can be estimated.

The purity of the carbon dioxide thus recovered is usually 98 to 99% by volume, or 99.0 to 99.9% by volume when more appropriately and stably performed, and is a high purity material for synthetic materials of chemicals or polymers, cold foods for food freezing, and the like. It is used as. In addition, it is also possible to sequester and store the recovered carbon dioxide under the ground which is currently being developed.

[Example]

Next, although an Example demonstrates this invention in detail, this invention is not limited to this Example.

Example  One

A glass gas washing bottle was immersed in a constant temperature water tank set so that the temperature of the liquid was 40 ° C, and 55% by weight of IPAE (Tokyo Kasei reagent) and sufflon S which was a nonionic perfluoro compound as a surfactant. 50 ml of an aqueous solution (absorption liquid) containing -141 (manufactured by AGC Seimi Chemical Co., Ltd.) at a weight concentration of 100 ppm was charged. The surface tension at 25 ° C. of the absorbent liquid before the absorption operation was 25 mN / m as measured by Kyowa Kaimen Kagaku Co., Ltd. Drop Master 300. In this liquid, a glass filter having a surface roughness of 100 µm and a diameter of 13 mm was passed through, and a mixed gas containing 20% by volume of carbon dioxide and 80% by volume of nitrogen was dispersed in a bubble state at an atmospheric pressure of 0.7 L / min. Absorbed for a minute.

The carbon dioxide concentration in the gas at the absorption inlet and the absorption liquid outlet was continuously measured with an infrared carbon dioxide meter (HORIBA GAS ANALYZER VA-3000), and the carbon dioxide absorption amount was measured from the difference in the carbon dioxide flow rates at the inlet and the outlet. If necessary, the amount of inorganic carbon in the absorbent liquid was measured by a gas chromatograph type total organic carbon system (SHIMADZU TOC-VCSH) and compared with a value calculated from an infrared carbon dioxide meter. Saturated water absorption was made into the quantity at the time when the carbon dioxide concentration of an absorption liquid outlet is equal to the carbon dioxide concentration of an inlet. Absorption rate changes with absorption amount, but was measured and compared on the basis of the absorption rate at the time of absorbing 1/2 of saturated absorption amount.

Subsequently, the liquid temperature was raised to 70 degreeC for several minutes in the same gas stream, and the carbon dioxide desorption amount was measured on the same conditions for 60 minutes. The carbon dioxide saturated absorption amount at 40 ° C was 145.5 g / L, and the absorption rate at the time of half absorption of the saturated absorption amount was 4.8 g / L / min. Carbon dioxide desorption at 70 ° C. was 78.5 g / L. The purity of the recovered carbon dioxide was 99.8%.

The calorific value is injected by a differential thermal calorimeter (SETARAM Co., Ltd. DRC Evolution) with two equally shaped absorbers with stirrer to inject a predetermined amount of carbon dioxide into only one reactor at 40 ° C, and two reactors therebetween. It measured by the difference of calorific value in inside.

Example  2, 3

Instead of an aqueous solution containing 55% by weight of IPAE and 100 ppm of S-141, 60% by weight and 70% by weight of IPAE were included, respectively, and 100 ppm by weight of 150 ppm by weight of Suplon S-141 as a surfactant. Except having used the aqueous solution mentioned above, it carried out similarly to Example 1, and measured the saturated absorption amount, absorption rate, calorific value, and desorption amount of carbon dioxide. The surface tension of the absorbent liquid containing surfactant was 24 and 23 mN / m, respectively. The saturated carbon dioxide uptake at 40 ° C. was 158.5 g / l and 162.7 g / l, respectively, and the absorption rates were 4.7 g / l / min and 4.4 g / l / min, and the carbon dioxide desorption at 70 ° C. was 87.5 g / L and 89.5 g, respectively. / L.

Example  4 to 6

The alkyl group of the alkylaminoalcohol was prepared in the same manner as in Example 2 except that the alkyl group of the alkylaminoalcohol was changed to the normal butyl group (n-BAE), the isobutyl group (IBAE), and the normal pentyl group (n-PEAE) instead of the isopropyl group. Saturated water absorption, water absorption rate, calorific value and desorption amount were measured. In addition, in Example 5 using IBAE, 200 ppm of Triton X which is a nonionic polyoxyethylene alkyl ether was used as a surfactant by weight concentration. The surface tension of each absorbent liquid was 22, 25, 23 mN / m.

Example  7, 8

Instead of 100 ppm of S-141, in Example 7, bisulfurized Seflon S-131 was added, and in Example 8, non-ionic polyoxyethylene alkyl ether was added in a concentration of 150 ppm and 250 ppm, respectively. In the same manner as in Example 2, the saturation absorption amount, absorption rate, calorific value and desorption amount of carbon dioxide were measured. Each surface tension was 26, 24 mN / m.

Example  9

Except having made the addition amount of surfactant into 1500 ppm by weight concentration instead of 100 ppm, it carried out similarly to Example 2, and measured the saturated absorption amount, absorption rate, calorific value, and desorption amount of carbon dioxide. The surface tension in this case was 22 mN / m.

Example  10

The saturation absorption amount, absorption rate, calorific value and desorption amount of carbon dioxide were measured in the same manner as in Example 2 except that the amount of the surfactant added was 20 ppm by weight instead of 100 ppm. The surface tension in this case was 30 mN / m.

Comparative example  1 to 3

Saturated absorption amount, absorption rate, calorific value of carbon dioxide in the same manner as in Example 1 except that an aqueous solution containing only IPAE 30, 55, 60% by weight was used instead of an aqueous solution containing 55% by weight of IPAE and 100 ppm of S-141. Desorption amount was measured. The surface tensions in this case were 55, 48 and 40 mN / m, respectively.

Comparative example  4 to 6

Except having used the aqueous solution which did not add surfactant, it carried out similarly to Examples 4-6, and measured the saturated absorption amount, absorption rate, calorific value, and desorption amount of carbon dioxide about Comparative Examples 4-6, respectively. In this case, the surface tensions were 45, 49, and 43 mN / m, respectively.

Comparative example  7

Instead of using an aqueous solution containing 55% by weight of IPAE and 100 ppm of S-141, 3% by weight of piperazine was added to an aqueous solution containing 52% by weight of IPAE, thereby using an aqueous solution having a total weight of amine of 55% by weight. In the same manner as in Example 1, the saturated absorption amount, absorption rate, calorific value and desorption amount of carbon dioxide were measured. Piperazine is known as a reactive activator in the absorption of carbon dioxide in aqueous alkanolamine solutions, and has an effect of improving the saturated absorption amount and the absorption rate.

The results obtained in Examples 1 to 10 and Comparative Examples 1 to 7 are shown in Tables 1 and 2. In addition,% in a table | surface represents weight%.

(Example 1)

From the above results, in Example 1, the saturation absorption amount and the desorption amount per unit absorption liquid are increased by high concentration compared with Comparative Example 1 of IPAE 30% by weight. Moreover, by addition of surfactant, the absorption rate also became higher than 3.2 g / l of the comparative example 2 of the IPAE density | concentration same as 4.8 g / L, and the effect by the addition of surfactant was confirmed. Moreover, compared with the comparative example 1, the calorific value per mole of carbon dioxide is falling and the effect by high concentration was confirmed.

(Examples 2 and 3)

From the above results, the absorption rate slightly decreased at 70% by weight of IPAE of Example 3, but the saturation absorption amount and the desorption amount were also increased in comparison with Example 2, and the effect of the performance improvement due to the high concentration was confirmed.

In addition, compared with Comparative Example 3, the highly concentrated absorbent liquids of Examples 2 and 3 had a large amount of desorption under the same desorption conditions at 70 ° C., and the recovery of carbon dioxide per cycle of absorption and desorption was high. As a result, it has an effect which leads to a reduction of recovery energy.

(Examples 4 to 6)

When the carbon chain length of the alkyl group is 4 or 5, the saturated absorption amount per unit absorption liquid is lowered by the influence of molecular weight, but the molar ratio of the absorption amount per amine with molecular weight correction is IPAE, n-BAE, IBAE, and n-PEAE, respectively. 0.62, 0.63, 0.62, and 0.64 were almost the same, and it turned out that the effect equivalent to an isopropyl group is obtained. Moreover, it was confirmed that high performance was shown also with respect to the comparative example 4 thru | or 6 which correspond also about a water absorption rate and a desorption amount.

(Example 7, 8)

Compared with Example 2 (Suplon S-141), the saturated water absorption is slightly lowered, but the absorption rate and the amount of desorption are almost the same, and have an effect equivalent to that of S-141. In addition, the calorific value was also at the same level as in Example 2, and no particular increase was observed.

(Example 9)

Compared with Example 2, although the saturation absorption amount and absorption rate slightly decreased, they exhibited higher performance than Comparative Example 3 without adding a surfactant, and the effect was confirmed. However, in this addition amount, foaming was observed with the progress of absorption of carbon dioxide, and from the viewpoint of operability, it was difficult to increase the addition amount more than this.

(Example 10)

Compared with Example 2, although the saturation absorption amount and absorption rate slightly decreased, they exhibited higher performance than Comparative Example 3 without adding a surfactant, and the effect was confirmed.

(Comparative Examples 1 to 3)

At a low concentration of 30% by weight, the absorption rate is high, but at 60% by weight, a significant decrease in the absorption rate is observed. As a result, it is understood that both the saturated absorption amount and the desorption amount have low values. Is difficult.

(Comparative Examples 4 to 6)

Comparative Examples 4 to 6 are conditions under which no surfactant is added to the absorbent liquids corresponding to Examples 4 to 6, but are separated from the corresponding examples in terms of saturated absorption amount, absorption rate and desorption amount. From this, the addition effect of surfactant was observed also in hindered amine other than IPAE.

(Comparative Example 7)

From the above results, the addition of the reactive activator showed an improvement in the saturated absorption amount and the absorption rate than the aqueous solution in IPAE alone, compared with the comparative example 2, but the surface tension at 25 ° C. was 45 mN / m and the addition of the reactive activator. The effect can be said to be a separate effect from the effect by the lowering of the surface tension. On the other hand, in the absorbent liquid containing a reactive activator such as piperazine, the calorific value is increased, which does not lead to a decrease in the recovery energy of carbon dioxide. It was found to be advantageous.

Claims (7)

An aqueous solution for absorbing and recovering carbon dioxide from a gas containing carbon dioxide, comprising 50 to 70% by weight of a secondary amine compound represented by the formula (1) and a surfactant.
≪ Formula 1 >

(Wherein R represents a linear or branched alkyl group having 3 to 5 carbon atoms) The aqueous solution according to claim 1, wherein the weight concentration of the surfactant is 10 to 1500 ppm. The aqueous solution according to claim 1, wherein R is an isopropyl group or an n-butyl group, and the surfactant is a compound having a nonionic perfluoroalkyl group. The aqueous solution according to claim 1, wherein R is an isopropyl group or n-butyl group, and the surfactant is a compound having an amphoteric perfluoroalkyl group. The aqueous solution according to claim 1, wherein R is an isopropyl group or n-butyl group, and the surfactant is a nonionic polyoxyethylene alkyl ether compound. The aqueous solution according to claim 1, wherein the surface tension at 25 ° C is 30 mN / m or less. (1) contacting the aqueous solution of paragraph 1 with a gas containing carbon dioxide to absorb carbon dioxide from the gas, and
(2) A step of desorption and recovery of carbon dioxide by heating the aqueous solution absorbed in carbon dioxide obtained in the above (1)
Carbon dioxide absorption and recovery method comprising a.